docs: def output_iface(gandi, iface, datacenters, vms, output_keys, justify=10):
      """ Helper to output an iface information."""
      output_generic(gandi, iface, output_keys, justify)
  
      if 'vm' in output_keys:
          vm_name = vms.get(iface['vm_id'], {}).get('hostname')
          if vm_name:
              output_line(gandi, 'vm', vm_name, justify)
  
      if 'dc' in output_keys:
          for dc in datacenters:
              if dc['id'] == iface.get('datacenter_id',
                                       iface.get('datacenter', {}).get('id')):
                  dc_name = dc.get('dc_code', dc.get('iso', ''))
                  break
  
          output_line(gandi, 'datacenter', dc_name, justify)
  
      if 'vlan_' in output_keys:
          vlan = iface.get('vlan') or {}
          output_line(gandi, 'vlan', vlan.get('name', '-'), justify)